Molecular Analysis of Oculocutaneous Albinism Patients in Korea

BACKGROUND: Oculocutaneous albinism (OCA) is a genetic disorder of the melanin pigment system in which melanin synthesis is reduced or absent in the skin, hair, and eyes. OCA is classified into two major types, and tyrosinase-related OCA can be produced by mutations of the structural gene for tyrosinase enzyme (TYR gene). OBJECTIVE: The purpose of this study was to analyze the segregation of mutant alleles of the TYR gene in tyrosinase-negative and tyrosinase-positive Korean OCA patients and families. METHODS: We amplified exon I, II, and III of the TYR gene of Korean OCA patients and their families by polymerase chain reactions (PCR), and analyzed the mutations by restriction fragment length polymorphism (RFLP) analysis in exon I and single-strand conformation polymorphism (SSCP) analyses in exon II and exon III. RESULTS: Two tyrosinase-negative cases showed mutations in exon I. Four tyrosinase-nega-tive cases and one tyrosinase-positive case showed mutations in exon II, and one tyrosinase-neg- ative case showed mutations in exon III. In summary, we found three kinds of mutation in four tyrosinase-negative OCA patients and one tyrsinase-positive OCA patient. CONCLUSIONS: RFLP and SSCP analysis can provide a basis for a rapid and sensitive screening system to detect TYR gene mutations of Korean OCA patients and their families.

A Study on the Tyrosinase Related to the Albinism / 체질인류학회지

The gene for tyrosinase has been mapped to the long arm of chromosome 11 at 11q14-21. The gene is at least 50Kb in length and its coding region is divided into five exons. Until now several mutations of the tyrosinase gene have been identifed in patient with typical oculocutaneous albinism (OCA) who are responsible for tyrosinase negative OCA. It may be possible to determine the types of OCA by measuring the hairbulb tyrosinase activity. Hairbulb tyrosinase activity was examined in a Korean albino to determine the type of OCA. And also tyrosinase assay was carried out in normally pigmented individuals and all members of a Korean albino's family to examine the tyrosinase activities. Five exons of tyrosinase gene from a Korean albino were amplified by polymerase chain reaction. Each amplified exon segments were independently subcloned and DNA sequences of clones were determined. The results obtained were as follows : 1. A Korean albino had no measurable hairbulb tyrosinase activity and was identified as type IA (tyrosinase negative) oculocutaneous albinism. 2. Normally pigmented individuals had different ranges of hairbulb tyrosinase activity. 3. A Korean albino had two single base insertions within exon V (between 337bp and 338bp, 353bp and 354bp) of tyrosinase gene. These insertional mutations might disrupt tyrosinase function and were associated with a total lack of melanin biosynthesis.